support auto create missing items in replace operation

[maxyurk]

support auto create missing items in replace operation
For example given doc:

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
</project>

And diff patch:

<diff>
    <replace sel="/project[@version='4']/component[@name='GOROOT']/inner/@url">file://$PROJECT_DIR$/.ting/bin/go</replace>
</diff>

Result:

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
    <component name="GOROOT">
        <inner url="file://$PROJECT_DIR$/.ting/bin/go"/>
    </component>
</project>

Note that not only component and inner are created and url value is set, but component also has the name attribute.

Should be opt-in as it's not standard.

[maxyurk]

done